Obviously not a world-shaking discussion, but maybe one with a bit more relevance than at first glance. Draper’s character was quasi-hip (screwing around with a bohemian Greenwich Village girl, checking out Antonioni pictures, reading Frank O’Hara, though always a little befuddled by them) in the late 50s and early 60s. It was useful to his profession and it satisfied some of his own restlessness and curiosity. But then things accelerated. In Sunday’s episode, he thought he already knew what the Beatles were about, because he’d had a handle on them a year or two earlier as a particularly inventive teen-pop band. That’s not an unreasonable expectation most of the time – two decades later, if you had a pretty good idea what Thriller was, you weren’t deeply clueless if you didn’t pay close attention to the differences in Bad. But in the mid-sixties, the centre of generational gravity was sliding much faster, and the quasi-hip Draper of his mid-30s becomes unfairly, upsettingly much older – the “Mr. Jones” Draper of 40.

As the show slips from the “forgotten Sixties” in which it began to the familiar later Sixties of a million TV specials, it hazards losing its subtlety and surprise. (This season has compensated by broadening its set pieces, and I’ve personally enjoyed that, but the risks are all visible.) But perhaps not if it keeps its attention on another allegorical level – when it comes to that kind of generational-shift velocity, I think the equivalent is the period we’re in right now. It’s one of those times when looking away for a year is like missing half a decade.

For one thing the “millennial” “echo boom” is the largest demographic group since the Baby Boom, by far. So it’s got that parallel momentum. But of course its salient cultural mover and marker is not music nearly so much as technology – “When did music get so important?” Draper asks, just as I often find myself asking, “When did music get so much less important?” – because the young adults coming of age now are the first really to grow up with the Internet. As a relative Don to their collective Megan (his much younger, hipper wife), I haven’t quite yet encountered my “Tomorrow Never Knows” watershed of bafflement, although I do suspect that the broader significance of Tumblr will always elude me. But I see it nearing.

Indeed, I think it’s one of the things going on with the comparable way-too-much-talked-aboutness of Lena Dunham’s Girls – that beyond the legit (but also sexist-double-standard) complaints about its white, wealthy, urban privilege, there’s also a disconnect between many observers and the part of the culture that it’s coming from.

In the way that someone of Draper’s generation was dumbfounded and annoyed by the boomer kids’ blithe shrugging off of dutifulness and pragmatism, I think some of Girls critics are having trouble distinguishing between the privileged part of its aesthetic and the part that’s really about being post-privacy and about navigating a life in which you are always already over-exposed. Or about being aware how fast things are going and having an undignified kind of haste about getting ahead of that curve. It reads as narcissism, in both cases. And youth is always narcissistic (although it is also often generous).

That’s why Girls compels me, even though I don’t find most of its jokes as funny as some viewers appear to. (It works better for me as a skewed drama than a comedy.) And it’s what I hope Mad Men could use its time exploring rather than running down the clock with swingin’ Sixties cliches – the other side of the Sixties myth: the pain of adjusting, the melancholy of being left behind, the Zen of giving up on being cool, the possible benefits of getting very confused, the rehearsal for mortality that is falling out of touch. That’s an understatement worth making.